Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus having a variable density image formation mode of controlling a supply amount of developer to be supplied to an image bearing member by a developer supply member.
Description of the Related Art
There is a color gamut as one of the image quality indices for an image forming apparatus. The color gamut for the image forming apparatus refers to a color reproduction range of colors that can be output by the image forming apparatus, and a wider color gamut means a wider color reproduction range and a higher superiority of the image forming apparatus. As a method of expanding the color gamut, it is conceivable to employ, for example, a method of separately adding developers of four dark colors of Y, M, C, and K to developers of four colors of Y, M, C, and K or a method of increasing the amount of developer on a recording material. For example, in Japanese Patent Application Laid-Open No. H08-227222, there is disclosed a proposal of adjusting the hue of a secondary color by changing the rotation speed of the developer supply member. The proposal aims at hue adjustment and does not aim at increasing the amount of developer on a recording material, but it is possible to widen the color gamut by applying this technology. That is, it is possible to increase the amount of developer by increasing the rotation speed of the developer supply member.
Meanwhile, there is also a demand of a user for suppressing toner consumption even at the expense of the color gamut. To meet such a demand, for example, the configuration of Japanese Patent Application Laid-Open No. H08-227222 can be employed to suppress the toner consumption by reducing the rotation speed of the developer supply member.
However, the related art has the following problems. In the method of separately adding developers of four dark colors of Y, M, C, and K to developers of four colors of Y, M, C, and K, the image forming apparatus is increased in size due to the addition of the developers. In addition, in the related art, the wear of toner and members progresses when the rotation speed is maintained at a high level, and hence it is preferred to provide a dedicated image formation mode as a wide color gamut image formation mode. However, a color balance is lost in the wide color gamut image formation mode without an image formation condition dedicated to this mode. It is also conceivable to provide a toner consumption saving mode for a user who wishes to extend the life of cartridges by suppressing the toner consumption. However, in the same manner as in the wide color gamut image formation mode, the color balance is also lost in the toner consumption saving mode without an image formation condition dedicated to this mode. In order to obtain the image formation condition dedicated to each mode, the hue adjustment is required for each image formation mode, which increases the downtime of the image forming apparatus for that purpose.